Bounce email

A bounce email occurs when an accepted email is rejected due to an error. This serves to inform the sender of the original email about the problem.

Misdirected bounce email

A bounce email is misdirected if the sender's address was faked and the returned bounce email therefore reaches someone who did not send the original email.
This means that the wrong person is informed of an error that was not caused by them.

MX / MX record

MX is short for Mail Exchanger, referring to the entry in the DNS (Domain Name System). This entry specifies the mail server responsible for the domain.
For example, the command nslookup -q=mx rz.rwth-aachen.de can be used to query the mail exchange records of the IT Center of RWTH Aachen University.